DESCRIPTION (adapted from the application) Broad, long-term objectives: To acquire research skills in a richly mentored environment that will foster the development of a career in patient-oriented research. In conjunction with training in renal physiology, magnetic resonance (MR) physics, image analysis, and biostatistics, the research focus will be to improve methods for the diagnosis of renovascular disease. Health relatedness: Renovascular disease (RVD) is the most common potentially reversible cause of hypertension and progressive renal insufficiency in the US, yet present diagnostic tests are limited to either anatomic or physiologic tests. The degree of renal artery stenosis (RAS) detected at angiography does not directly correlate with the physiologic significance of the narrowing and hence does not accurately predict response to revascularization. MR angiography can provide an accurate minimally invasive method for identifying RAS, but is presently limited to anatomic assessments. We hypothesize that the development of MR techniques that can measure the physiologic consequences of stenoses will lead to improved diagnostic accuracy. Specific Aims/Methods: 1) To measure blood flow in the renal arteries using newly developed faster MR phase contrast flow quantification techniques (validated in phantoms) and to correlate patterns of velocity waveforms (akin to Doppler tracings) with severity of renal artery stenosis. 2) To develop MR methods to measure parameters of renal function including whole kidney and regional (cortex, medulla, collecting system) perfusion, glomerular filtration rate, and tracer kinetic parameters such as mean transit time. Ultra-low doses of Gd-DTPA contrast permit quantitative determinations of contrast concentration. To evaluate renal response independent of variation in cardiac output, injection rate, and dose, deconvolution of renal Gd-DTPA concentration-time curves will be performed using measured aortic input function. MR results will be compared with scintigraphic measures of renal function using gamma camera and blood sample methods with Tc-99m-DTPA. 3) To investigate the effects of angiotensin converting enzyme-inhibitor on renal artery flow and perfusion measurements. Following a period of technique optimization and validation, a comprehensive MR protocol will be tested in a population of patients with suspected RVD, and the diagnostic accuracy of MR measures of renal artery velocity waveforms, GFR, and intrarenal tracer kinetics will be compared with anatomic evaluation by renal MR angiography.